Network service providers and device manufacturers are continually challenged to deliver value and convenience to consumers by, for example, providing compelling network services. One aspect of delivering rich content from network services is to tailor the presentation of that content for the user's device, especially when the user's device is a mobile terminal with limited display area or user input mechanisms or bandwidth, such as a cellular telephone. Much content is delivered to desktop computers using the hypertext transfer protocol (HTTP) for exchanging messages between a service process on the network and a client process on the user's equipment. Desktop computers are highly capable devices often endowed with large display screens, fast network connections, large memories and powerful processors. The content, however, delivered from a service to client should be modified for efficient delivery and effective presentation on a mobile terminal, which often has limited bandwidth or display area or input mechanisms. Thus HTTP allows an HTTP client to indicate the capabilities of the user equipment (such as manufacturer, model number and operating system) in a user agent field of a header portion of the HTTP message. Many network service processes tailor the content of HTTP messages sent to the client process based on the information in the user agent field to improve the user experience of the service, e.g., by making the most relevant or interesting parts of the content more quickly presented and more easily viewed by the user, and discarding or relegating to less accessible areas other information of less relevance or interest.
Recently, some network operators have interjected their own modifications for HTTP messages between client processes on mobile devices and service providers on the network. Using a mechanism called transcoding, these network operators often attempt to request full HTTP content from service providers and reformat that full content for the user's equipment. In general, transcoding changes the HTTP header information, such as the user agent field, sent to the service provider. Thus the user experience is affected by a network operator unaware of the user experience envisioned by the service provider, and some services fail. Many service providers find this undesirable and damaging.